During the current (2008) fiscal year we accomplished the following:[unreadable] [unreadable] (1) Determined the contribution of E&#956; to establishing tissue-specific chromatin state prior to initiation of recombination, its role in sterile transcription through a 400 kb region and its effect on DH to JH recombination. E&#956;-deleted alleles exhibit a partially activated state characterized by normal depletion of H3K9me2 and gain of H34K4me2, but absence of H3 or H4 acetylation. These observations demonstrate an epigenetic hierarchy in tissue-specific locus activation.[unreadable] [unreadable] (2) We used BAC engineering to move E&#956; to different locations within the DH-C&#956; domain of IgH. These BACs were used to generate transgenic mice. The first group of potential founders are being bred for further analysis.[unreadable] [unreadable] (3) Completed analyzing the effects of the first step of recombination on chromatin structure in the IgH locus. We found localized alteration of activation modifications that provide a plausible mechanism for targeting VH gene recombination to the rearranged DJH junction.[unreadable] [unreadable] (4) Completed analyzing DNA methylation in the IgH locus before, and after, initiation of recombination. We found that DJH junctions undergo localized CpG de-methylation in normal pro-B cells. This effect was absent in E&#956;-deficient alleles indicating that de-methylation is directed by E&#956;.